EP 0 806 603 [U.S. Pat. No. 5,788,012] discloses a lubricant dispenser that has these features. A preset value is established for the dispensing time, namely the time to empty the reservoir. From this a microcontroller of the electronic controller calculates the required gas generation rate and controls the gas generator so as to achieve, or at least not to exceed, the set dispensing time for a standard temperature (typically room temperature, that is, approximately 20° C.). No consideration is given to the temperature effect on the gas generation rate and on the volume of lubricant dispensed per unit of time. When the lubricant dispenser is employed outdoors, the dispensing time actually achieved can deviate quite significantly from the preset value as a function of the climate, seasonally fluctuating temperatures, and changes in temperature due to the effects of the weather.
U.S. Pat. No. 5,968,325 describes a lubricant dispenser comprising a gas generator that makes gas spontaneously in a closed circuit without external energy. The gas generation rate, namely the generated gas volume per unit of time, is dependent on the electrical current and can be modified by an electrical resistance. This reference states that gas generation that is less strongly affected by temperature effects can be implemented if the electrical resistance of the gas-generating cell changes as a function of temperature—for which purpose PTC resistors are used whose resistance increases as the temperature rises. However, the compensation of temperature that is possible through the use of a PTC resistor still needs to be improved.